Pumpless combination instantaneous/storage water heater system

Abstract

A representatively pumpless water heater system has an instantaneous water heater coupled in series with a storage water heater by piping circuitry incorporating a bypass valve and a mixing valve and useable to route pressurized incoming cold water sequentially through the instantaneous and storage type heaters. A control system (1) operates the bypass valve to cause a selectively variable portion of the incoming cold water to bypass the instantaneous heater and flow to the mixing valve, and (2) operates the mixing valve to blend the bypassed cold water with hot water exiting the storage heater to maintain a predetermined temperature of heated water exiting the system. Another system embodiment adds a directional bypass valve operable by the control system to selectively divert to the mixing valve a portion of the heated water exiting the instantaneous heater for delivery to the storage heater.

1. Fluid heating apparatus comprising:
 an instantaneous fluid heater; 
 a fluid storage vessel; and 
 flow circuitry, interconnected between said instantaneous fluid heater and said fluid storage vessel, via which an incoming fluid may be sequentially flowed through said instantaneous fluid heater and said fluid storage vessel for discharge from said apparatus as heated fluid, said flow circuitry including (1) an incoming fluid bypass valve operable to cause a selectively variable portion of the incoming fluid to bypass said instantaneous fluid heater, and (2) a mixing valve connected in series with said incoming fluid bypass valve and operable to blend the bypassed fluid and heated fluid exiting said fluid storage vessel to maintain a predetermined temperature of heated fluid discharged from said apparatus. 
 
   
   
     2. The fluid heating apparatus of  claim 1  wherein:
 said instantaneous fluid heater is fuel-fired. 
 
   
   
     3. The fluid heating apparatus of  claim 1  further comprising:
 a heating structure selectively operable to add auxiliary heat to fluid in said fluid storage vessel. 
 
   
   
     4. The fluid heating apparatus of  claim 3  wherein:
 said heating structure is an electrical heating structure. 
 
   
   
     5. The fluid heating apparatus of  claim 1  further comprising:
 control apparatus for automatically controlling said incoming fluid bypass valve. 
 
   
   
     6. The fluid heating apparatus of  claim 5  wherein:
 said control apparatus is operative to control said incoming fluid bypass valve as a function of the temperature of fluid in said fluid storage vessel, the temperature of heating fluid being discharged from said instantaneous fluid heater, the temperature of heated fluid being discharged from said fluid heating apparatus, and the temperature of the incoming fluid. 
 
   
   
     7. Fluid heating apparatus comprising:
 an instantaneous fluid heater; 
 a fluid storage vessel; and 
 flow circuitry, interconnected between said instantaneous fluid heater and said fluid storage vessel, via which an incoming fluid may be sequentially flowed through said instantaneous fluid heater and said fluid storage vessel for discharge from said apparatus as heated fluid, said flow circuitry including (1) an incoming fluid bypass structure operable to cause a selectively variable portion of the incoming fluid to bypass said instantaneous fluid heater, and (2) a mixing structure operable to blend the bypassed fluid and heated fluid exiting said fluid storage vessel to maintain a predetermined temperature of heated fluid discharged from said apparatus, 
 said flow circuitry further including a directional fluid bypass structure operative to receive heated fluid exiting said instantaneous fluid heater and flow selectively variable portions of the exiting heated fluid respectively to said mixing structure and to said fluid storage vessel, and wherein 
 said mixing structure is further operable to blend fluid it receives from said directional fluid bypass structure with the bypassed fluid and the heated fluid exiting said fluid storage vessel to maintain said predetermined temperature of heated fluid discharged from said apparatus. 
 
   
   
     8. The fluid heating apparatus of  claim 7  further comprising:
 control apparatus for automatically controlling said directional fluid bypass structure. 
 
   
   
     9. The fluid heating apparatus of  claim 8  wherein:
 said control apparatus is operative to control said directional fluid bypass structure as a function of the temperature of fluid in said fluid storage vessel, the temperature of heated fluid being discharged from said instantaneous fluid heater, and the temperature of heated fluid being discharged from said fluid heating apparatus. 
 
   
   
     10. The fluid heating apparatus of  claim 9  wherein:
 said instantaneous fluid heater has a fuel burner portion, and 
 said control apparatus is further operative to control said fuel burner portion. 
 
   
   
     11. The fluid heating apparatus of  claim 1  wherein:
 said fluid heating apparatus is of a pumpless construction. 
 
   
   
     12. The fluid heating apparatus of  claim 7  wherein:
 said fluid heating apparatus is of a pumpless construction. 
 
   
   
     13. Fluid heating apparatus comprising:
 an instantaneous fluid heater; 
 a fluid storage vessel; and 
 flow circuitry, interconnected between said instantaneous fluid heater and said fluid storage vessel, via which an incoming fluid may be sequentially flowed through said instantaneous fluid heater and said fluid storage vessel for discharge from said apparatus as heated fluid, said flow circuitry including:
 (1) a directional fluid bypass structure operative to receive heated fluid exiting said instantaneous fluid heater and flow selectively variable portions of the exiting heated fluid respectively into said fluid storage vessel and through a path bypassing said fluid storage vessel, and 
 (2) a mixing structure operative to receive and blend flows of the incoming fluid, the fluid bypassing said fluid storage vessel, and heated fluid exiting said fluid storage vessel to maintain a predetermined temperature of heated fluid discharged from said apparatus. 
 
 
   
   
     14. The fluid heating apparatus of  claim 13  further comprising:
 a heating structure selectively operable to add auxiliary heat to fluid in said fluid storage vessel. 
 
   
   
     15. The fluid heating apparatus of  claim 14  wherein:
 said heating structure is an electrical heating structure. 
 
   
   
     16. The fluid heating apparatus of  claim 13  wherein:
 said instantaneous fluid heater is fuel-fired. 
 
   
   
     17. The fluid heating apparatus of  claim 13  further comprising:
 control apparatus for automatically controlling said directional fluid bypass structure and said mixing structure. 
 
   
   
     18. The fluid heating apparatus of  claim 17  wherein:
 said control apparatus is operative to automatically control said directional fluid bypass structure and said mixing structure as a function of the temperature of fluid in said fluid storage vessel, the temperature of heated fluid being discharged from said instantaneous fluid heater, and the temperature of heated fluid being discharged from said fluid heating apparatus. 
 
   
   
     19. The fluid heating apparatus of  claim 18  wherein:
 said instantaneous fluid heater has a fuel burner portion, and 
 said control apparatus is further operative to control said fuel burner portion. 
 
   
   
     20. The fluid heating apparatus of  claim 13  wherein:
 said fluid heating apparatus is of a pumpless construction. 
 
   
   
     21. A combination instantaneous/storage type water heater system comprising:
 a fuel-fired instantaneous water heater; 
 a storage type water heater; 
 piping interconnecting said instantaneous and storage type water heaters in series and via which pressurized incoming water to be heated may be flowed sequentially through said instantaneous and storage type water heaters; 
 an incoming water bypass valve interconnected in said piping and operable to cause a selectively variable portion of the pressurized incoming water to bypass said instantaneous water heater; 
 a mixing valve interconnected in said piping and operable to blend the bypassed water and heated water exiting said fluid storage vessel to maintain a predetermined temperature of heated fluid discharged from said water heater system; and 
 control apparatus for automatically controlling said incoming water bypass valve and said mixing valve. 
 
   
   
     22. The water heater system of  claim 21  wherein:
 said water heater system is of a pumpless construction. 
 
   
   
     23. The water heater system of  claim 21  further comprising:
 a directional bypass valve interconnected in said piping and operative to receive heated water exiting said instantaneous water heater and flow selectively variable portions of the exiting heated water respectively to said mixing valve and to said storage type water heater, and wherein 
 said mixing valve is further operable to blend water it receives from said directional bypass valve with the bypassed incoming water and the heated water exiting said storage type water heater to maintain said predetermined temperature of heated water discharged from said water heater system, and 
 said control apparatus is further operable to automatically control said directional bypass valve. 
 
   
   
     24. The water heater system of  claim 23  wherein:
 said water heater system is of a pumpless construction. 
 
   
   
     25. The water heater system of  claim 21  wherein:
 said storage type water heater comprises a water storage tank and an electrical heating structure selectively operative to heat water disposed within said water storage tank.